Rotor for multistage high-speed engines



P. SPIESS.

ROTOR FOR MULTISTAGE HIGH SPEED ENGINES- APPLICATION FILED MAR. 23. 1920.

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Further,

UNITED V STATES PATENT OFFICE. I

PAUL srmss, or 21131011, swrr znammb.

ROTOR FOR MULTISTAGE HIGH-SPEED ENGINES.

Specification of Letters LPatent.

Application and March 23, .1920. Serial No. 368,120.

able others skilled inthe art to which it ap pertains to make and use the same, reference being had to the accompanying drawlng, and to letters or figures of reference marked thereon, which form a part of thls specification.

This invention relates to improvements in rotors for multistage high-speed engines and particularly to rotors of the disk-type for steam-turb1nes. Y

The constant increase of the e "ne speed .for given outputs, particularly with steamturbines, causes an increased action of the centrifugal forces on the rotor of such engines. In a rotor of the disk-type, with disks mounted on a shaft and provided with central bores for that purpose, the disks are subjected to very high stresses, particularly at the circumference of the bore in the boss. these constructions necessitate large diameters of the bosses and in consequence thereof show large leakage losses at said bosses. v

Referring to the drawings in wh1ch llke parts are similarly designatedv Figure l is a diagram showing the mfluence of a bore through a disk.

Fig. 2 is a vertical central section show ing one form of my invention, and

Fig. 3 is a like view showlng a modlfication. Y

The influence of a bore on the distribution of strain in a disk is shown in Fig. 1 ofv the accompanying drawing. Curve 1 of the-diagram represents the distribution of strain in a disk provided with'a central bore. The abscissae of this diagram are the radii of the various centers of the merid-- ian-sections of a disk measured in centimeters and the ordinates are the tangential stresses in kilograms per square centimeter'produced in the diiferentsections of a disk under normal working conditions. The radius of the bore of the disk is 1' The greatest s rain caused by the centrifugal force is gt the circumference of the Patented D ec.13, 1921'.

bore, that is the tangential strain .9 shown in the dia. am. 'Even in the caseof disks fitted with broad and thick bosses this strain 1s very high. The second curve II represents the distribution of strain in a disk without a, central bore, wherein the thickness in the center of the disk may only be half as large as the width of the boss in the previously mentioned case. It will readily be seen from the diagram that the maximum strain S is less than half of the maximal strain S of the bored disk. In view of these facts it has been proposed to produce the rotors of high speed engines and partic-v ularly of steam turbines of a single solid "piece and to efl'ect the necessary recesses by turning them off the'solid mass. The manufacture of such a rotor is very tedious, it takes up much time and is very expensive.

. Moreover the danger always exists that the interior of such a solid mass has-not the desired uniform structure and strength.

Such a mass may be porous in'p-laces which.

deficiency may not be detected until the last stage of manufacture with the result that the whole time and costs involved up till then are lost. a

These disadvantages are overcome by the present invention. According to this invention the rotor of multistage high-speed engines, particularly of steam-turbines of the disk type, is produced by shaping each disk as a body of uniform strength of a solid mass. Any bore near the center of a disk is avoided and the disks are joinedtogether by means of gripping joints. This method of joining may be carried out in many ways, for instance two adjacent disks .may be provided with pins coaxially arranged and ydirected against each other, one of. the pins being hollow and fitting over the other. The pins may then be pressed one into the other to produce a shrinking strain. Further the pins pressed one into the other may be secured against radial and axial displacement by means of transverse fitting bolts. For the purpose of increasing the moment of inertia on which the deflection depends, that side ofthe first disk provided with the smaller pin maybe shaped to project over the end of the hollow pin of the other disk in such a Way that it exerts on said end a radial strain directed toward the axis.

. An exemplification of this invention adapted for a rotor of a free-jet steam-tun shape of a disk of uniform strength is shown by, dotted lines a and 1) near the center line of disk 1 and 2. It will be seen from the drawing that said shape is not intersected by holes or notches. The disk 1 1s forged in one piece with the adjoining shaft 6. Disk 1 is on its right hand side provided with a solid pin 7, which is inserted into a hollow pin 8 of the next adjacent disk 2. The out- 7 side diameter of the solid pin 7 and the bore of the hollow pin 8 may be dimensioned in such a way that by pressing the hollow pin 8 over the solid pin 7 the two disks are held together by a shrinking stress sufficlent for working conditions. 4

A further example of joining two ad acent disks is shown in the connection of dlsks 3 and 4'.- In this exemplification disk 4' is fitted with a hollow pin 14 into which the solid pin 15.01 disk 3' is inserted. D1sk 3 is provided with a laterally projecting fillet 16 which fits on the left end of the hollow pin 14 and exerts on that end'a radial inwardly directed pressure. Without this fillet the moment of inertia of disk 3' in a plane vertical to the axis of rotation and passing through the root of pin l5, i. e. in the section III-III of Fig. 3, is approximately the same as that of pin 15. In spite of the small thickness of its wall the hollow pin 14 can have a moment of inertia with regard to an axis vertical of the axis of rotation,.which is considerably greater'than that of the solid pin 15, because its sectional elements are at a greater distance from the axis. Section IIIIII is therefore the weakest part of the joint. On account of the radial pressure ex erted by the fillet 16 on the hollow pin 14, pins 14 and 15 and fillet 16 in the section IIIIII may be considered as one solid part with regard to their resisting power against deflection and the moment of inertia of that part is greater than that of pin 15. The fillet 16 acting together with the pins 14 and 15 contributes essentially to the rigidity of the joint and counteracts the deflection.

To prevent the inserted pins of the disks 1 and 2, 2 and 3, 3 and 4 from being turned against or distanced from each other on account of the varying bending stress and vibration, fitting bolts may be provided passing transversely through the pins. In Fig. 2 two fitting bolts 31 and 32 are arranged at an angle 0 90 to each other and are perpendicular to the axis of the shaft at a certain axial distance from each other. The fitting bolt 32 Fig. 3, is also perpendicular to the axis of the rotors.

Rotors according to the present invention have the same advantages as the rotors made of one solid piece, 2'. e. of smaller stresses and smaller leakage losses at the guide-wheel bosses but they are simpler and more reliable as regards manufacture and uniformity of structure.

I claim:

1. In a rotor of the disk-type for highspeed turbines, pumps and compressors, comprising a plurality of disk shaped rotor elements each consisting of a body of uniform strength the planes thereof being imperforate, a hollow pin provided on one side of a disk coaxially and integral therewith, a solid pin provided on the adjacent side of the adjacent disk coaxial and integral therewith, the bore of said hollow pin being slightly smaller than the outside diameter of the solid pin, the solid pin of one element inserted in the hollow pin of an adjacent element and holding the joint in position by radial compression stresses for uniting the single elements into a rotor.

2. In a rotor of the disk-type for highspeed turbines, pumps and compressors, a plurality of rotor elements shaped as bodies of uniform strength, the plane of said shape being imperforate, a hollow pin provided on one side of an element and coaxial and integral therewith, a solid pin provided on the adjacent side of the adjacent element coaxial and integral therewith, the bore of said hollow pin being slightly smaller than the outside diameter of said solid pin so that the solid pin when inserted into the hollow pin is held in position by radially acting compression stresses whereby a rigid rotor is formed and a rim provided on the side of the. element carrying the solid pin coaxial with the latter and projecting over and gripping the end of the hollow pin of the adjacent element to form a rigid connection by which the moment of inertia on which the deflection of the joint depends is increased.

3. In a rotor of the disk-type for highspeed turbines, pumps and compressors, a plurality of disk shaped rotor elements of uniform strength, the planes of said elements being imperforate, a hollow pin provided on one side of an element coaxial and integral therewith, a solid pin provided on the adjacent side of the adjacent element 00 axial and integral therewith, the bore of said hollow pin being slightly smaller than the outside diameter of the solid pin whereby the joint is held in position by radially acting compression stresses uniting the elements into a rotor and bolts passing radially through the interfitted pins.

4. In a rotor of the disk-type for highspeed turbines, pumps and compressors, a plurality of disk-shaped rotor elements, shaped as bodies of uniform strength, and imperforate, a hollow pin provided on one side of an element coaxial and integral therewith, a solid pin provided on the adjacent side of the ad'acent element coaxial and integral therewith, the bore of said hollow pin being slightly smaller than the outside diameter of said solid pin to hold the solid pin in the hollow pin in position by radially acting compression stresses whereby a rigid rotor is formed, and a rim provided on the side of the element carrying the solid pin, coaxial with the latter and projecting over and gripping the end of the hollow pin of the adjacent element, thereby forming a rigid connection by which the moment of inertia on which the deflection of the joint depends is increased, and bolts passing radially through the interfitting ins. p 5. A rotor disk for high speed turbines, pumps-and compressors, which comprises an imperforate runner disk having a. solid pin as my invention, I have 6. A rotor disk for high speed turbines,

pumps and compressors, comprising an imperforate runner disk having a central solid pin on one side and a central hollow pin on the other side, said solid pin seated in a recess forming a circular fillet for receiving the end of a hollow pin on an adjacent disk.

7. A rotor disk for high speed turbines, pumps and compressors, comprising an im perforate runner disk having a solid pin projectin centrally from one side thereof and a ho low pin projecting centrally from. the other side thereof, said hollow .pin having a thickened conical end and said solid pin surrounded by a conical recess in one side of the disk for interfitting with the conical end of the pin of an adjacent disk.

In testimony that I claim the foregoing signed m name.

PAUL PIESS.. 

